(1) Field of the Invention:
The present invention relates to a method of purifying fatty acids in order to obtain fatty acids having excellent color and color stability.
(2) Description of the Prior Art:
There are generally known, as a method of purifying fatty acids, adsorption method using activated clay or active carbon, and further methods using polycarboxylic acid (Japanese Patent Laid Open Application No. 4,277/72), boric acid (U.S. Pat. No. 2,862,943), sulfuric acid (U.S. Pat. No. 3,489,779), boron trifluoride (U.S. Pat. No. 2,583,028), amino compound (U.S. Pat. No. 3,471,536), formaldehyde (U.S. Pat. No. 3,066,160), a combination system of an alkaline substance, hypophosphorous acid and boric acid (Japanese Patent Application Publication No. 16,506/71) and a combination system of organic amine and phenolic compound (Japanese Patent Application Publication No. 46,205/77 and No. 7,408/78). In these methods, a part of the coloring substances contained in fatty acid can be removed, but sufficiently light-colored fatty acid can not be obtained, and further impurities, which color due to heat, oxidation or acidic or basic reagent, can not be completely removed. Therefore, the fatty acids purified by the above described methods often color during storage and further the derivatives of the fatty acid often color. Moreover, some of the above described reagents are dangerous or poisonous.
The inventor has made various investigations for developing a method of purifying fatty acids, which is free from the drawbacks of the above described conventional methods, and found out a purification method having a high purification efficiency which can be carried out by the use of a safe and substantially non-toxic reagent.